Originator authentication using platform attestation

ABSTRACT

An originator device allows for a unique passphrase to be communicated to a service system. The originator device has a fixed token in which a unique platform identifier is recorded and a processor to generate a representation of the platform configuration. This representation is communicated to the registry service as a unique, platform-specific passphrase associated with the originator.

BACKGROUND

[0001] Most services require user identification. The method for proving the identity is authentication. The typical ways to provide authentication include but are not limited to authentication protocols and transmitted stored or user entered passphrase. This result of the authentication protocol or transmission of a passphrase serves as a credential proving identity. Examples of services that use these authentication methods are: LDAP, HTML documents, UDDI, etc.

[0002] For example, the Universal Description, Discovery and Integration (UDDI) architecture provides a service with which businesses can register and then utilize to publish their information as well as seek information about other businesses. LDAP stands for the Lightweight Directory Access Protocol that specifies how global directories should be structured. Directories using LDAP typically require the user to enter a user id and passphrase.

[0003] A possible pitfall for clients using these services is their vulnerability to attacks by hackers and impostors. Impostors could insert themselves into the process and usurp information, possibly sensitive, from both the client and the service. This could lead to such problems as theft of monies involved in transactions, identity theft and others.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Embodiments of the invention may be best understood by reading the disclosure with reference to the drawings, wherein:

[0005]FIG. 1 shows an embodiment of an registration interaction in accordance with the prior art.

[0006]FIG. 2 shows an embodiment of an registration interaction such as UDDI in accordance with embodiments of the present invention.

[0007]FIG. 3 shows an embodiment of a platform device.

[0008]FIG. 4 shows a flowchart of an embodiment of a method of registering with a service.

[0009]FIG. 5 shows a flowchart of an embodiment of a method of accessing a service by a client that has previously registered with the service.

[0010]FIG. 6 shows a flowchart of an alternative embodiment of a method of accessing a service by a client that has previously registered with the service.

[0011]FIG. 7 shows a flowchart of an alternative embodiment of a method of accessing a service by a client that has previously registered with the service.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] A typical interaction between a user/client and a service is shown in FIG. 1. The client A 10 registers with the service 14. The service may be one of several types of services, including UDDI, LDAP, etc. An impostor 12 could intercept the information transmitted between the service 14 and the client 10. This information could then be used to the impostor's advantage and the client's disadvantage, or the impostor could even enter the impostor's information into the service, taking the client's place.

[0013] In FIG. 2, however, the same process occurs, except that client A supplies some platform specific information with the user id and passphrase. For example, the client's platform has a unique platform identifier, typically part of the fixed token, as will be discussed in more detail with regards to FIG. 3. The fixed token is permanently affixed to the motherboard and has a 1:1 relationship with the platform. There are keys associated with the fixed token. Typically, keys are RSA keys, or Attestation Identity Keys (AIK). However, here is a 1:1 relationship between the keys and the platform, so these will be referred to as unique platform identifiers.

[0014] Because the unique platform identifier is supplied as part of the passphrase, only the user on that platform can access the service. This effectively prevents the impostors from being able to insert themselves into the interactions between the service 14 and the client 10.

[0015] An embodiment of a platform with a fixed-token capability as well as the capability to provide this unique passphrase is shown in FIG. 3. The platform 20 includes a processor 24, a fixed-token 22, a user interface 26 and communications port 28. The processor 24 could be any type of component that is capable of performing hash operations on data, including a general-purpose processor, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), or a field-programmable gate array (FPGA). Similarly, the fixed token 22 may be an integrated circuit or chip, or even part of another component, including the processor. As mentioned above, the fixed token is permanently affixed to the motherboard and has a 1:1 relationship with the platform.

[0016] Typically, AIKs are used to digitally sign the platform's configuration registers. For example, during a service interaction, the passphrase would be generated as a hash, also referred to as a representation, of the signed fixed-token platform configuration. The representation will more than likely be a hash of an attribute of the fixed token, such as unique keying information associated with the fixed token. Whenever the subscriber desires to interact with the service the authentication token originally sent from the service to the subscriber will include this information, making it non-guessable and platform specific. The passphrase hash may include data received from the originator as a password on user interface 26. The passphrase is communicated to the service through the communication port 28. The port 28 may be a communications port for a remote service such as an Ethernet port or modem port, or it may be simply a direct line to another component of the system for local communication.

[0017] The interactions with the service have two aspects. The first interaction is the initial registration with the service and the second is when the client desires to use the service. FIG. 4 shows a flowchart of an embodiment and options for the registration process with a service using a platform specific passphrase.

[0018] In a first embodiment, the client desiring registration with the service transmits a new user id at 30, a passphrase at 32 and the platform configuration register (PCR) values for the platform at 34. Typically, the platform configuration registers (PCRs) are populated upon platform initialization, such as power-up or re-boot. In one embodiment, the PCRs are populated by the system taking measurements to create data values that are then hashed. For example, an initial measurement may be a 64 Kbit measurement that is hashed to a 160-bit value. This 160 bit value is then extended to a PCR register by taking the current PCR register value, another 160 bit value, and concatenating them together. This 320-bit value is then hashed to a 160-bit value and the value is stored in the PCR. The service may have a specified number of PCR values that it requests from the client platform, or the client platform may specify. The implementation of the reading of the PCRs is left to the system designer.

[0019] In this embodiment, the unique platform identifier, such as the AIK or RSA key, is obtained at 36, and all of these values are transmitted for registration at 38. Note that transmission may involve a user voluntarily transmitting the value, or the service requesting the values, possibly without the user's knowledge. At 40, the service stores the passphrase, the PCR values, the unique platform ID and the user ID. In one embodiment the passphrase, PCR values and the platform ID may be bound to the user ID to allow for easier and faster access for subsequent interactions.

[0020] In another embodiment, the service receives or retrieves the unique platform ID and the user passphrase and associates them at 42. At 44, proof is then obtained that the association of the platform ID and the user ID associated with that passphrase is valid. This may be obtained in several ways but typically during the registration process while in or using some trusted environment. For example, the user could, using a telephone, convey validation information to a person involved in the registration. In this case the telephone is a trusted process in that it would be difficult to attack both the telephone system and the network simultaneously. Note that the use of a telephone is just intended as an example of a proving mechanism and is not intended to limit the scope of the claims. This will be discussed in more detail with regard to the interaction described with reference to FIG. 7.

[0021]FIGS. 5 and 6 show flowcharts of alternative embodiments of interacting with the service, based upon a registration process similar to that discussed in the first embodiment above. In FIG. 5, the process begins by the user starting the login process with the service. The user requests an authentication nonce from the service at 50. A nonce, as the term is used here, is an element intended for one-time use, such as a random number, a time stamp, or a counter, that is used in mathematical operations such as digital signature functions. At 52, the service generates the nonce, stores a copy of it and returns the nonce to the user. At 56, the client platform performs attestation, in which the platform is identified by a digitally signed reading of the PCR values. The unique platform ID is typically used to perform the digital signature.

[0022] At 58, the client acquires the user passphrase from the user and combines it with the attestation at 60. The service then verifies the passphrase at 62, the signature at 64 and the PCR values at 66. If all of those verify correctly, the service provides the user with a session token at 70 and the user interacts with the service.

[0023]FIG. 6 shows an alternative embodiment of an interaction based upon the first embodiment of registration discussed above. Similar to FIG. 5, the user requests an authentication nonce at 50, which the service generates, stores a copy and returns at 52. The client then gets the user passphrase at 58, combining the nonce and the passphrase into an attestation nonce at 71. This will typically be done by a hashing function, resulting in an attestation nonce, which is used in 56. This is similar to the attestation performed in the previous embodiment at 56, but the attestation provided will differ from the previous attestation.

[0024] At 60, the client sends the credential to the service. The service obtains the nonce and passphrase from storage at 72 and then uses them to derive the attestation nonce provided at 56 in 74. This is then verified by verifying the signature at 64 and the PCRs at 66. If the derived attestation nonce does not match the transmitted attestation nonce, or if either of the signature or the PCR values are different, the process will failure. If they are all valid, the session token is provided at 70.

[0025] In another embodiment of an interaction process, FIG. 7 demonstrates an interaction based upon the second registration embodiment discussed above. In that registration process, the unique platform ID, the passphrase and user ID were independently proved to be validly associated. In this embodiment, the user requests the authentication nonce at 50, and the service generates a nonce, stores a copy and returns it to the user at 52. When the service obtains the passphrase at 58, in this embodiment, it provides platform attestation at 80 based upon the attested passphrase proven during the registration process. The service then retrieves the nonce at 82 and proceeds with signature and PCR verification to provide the token at 70.

[0026] In the embodiments set forth above, which are intended only as examples, the service allows secure access to users based upon the platform from which the user seeks to gain access. The service receives a request for a nonce, generates the nonce, stores a copy and returns it to the user. The service then obtains a credential from the client, typically in the form of an attestation, verifies the signature and PCR values contained in or related to the credential and then passes a session token back to the user.

[0027] In this manner, unique platform identifiers may be used to secure the identity of the user. Interlopers can no longer access and falsify their identities without access to the physical platform used by the user during registration. While this may be inconvenient for many users who may roam from computer to computer for all interactions, it could be used by service providers such as financial institutions to require transactions of a certain type or level to be performed from the user's home computer.

[0028] Thus, although there has been described to this point a particular embodiment for a method and apparatus for providing secure service interactions, it is not intended that such specific references be considered as limitations upon the scope of this invention except in-so-far as set forth in the following claims. 

What is claimed is:
 1. An originator device, comprising: a fixed token to store a unique platform identifier; and a processor to generate a representation of a platform configuration; a user interface to allow a user to transmit a passphrase to the processor; and a port to allow the device to communicate the representation to a registry service.
 2. The device of claim 1, wherein the fixed token further comprises a set of platform configuration registers.
 3. The device of claim 1, wherein the representation further comprises a hash of attributes of the fixed token.
 4. The device of claim 2, wherein the representation further comprises a hash of attributes of the fixed token and the passphrase.
 5. The device of claim 1, wherein the representation further comprises a digital signature of the platform configuration.
 6. A registry system, the system comprising: a registry to receive registration requests from originators; and an originator device, wherein the originator device further comprises: a fixed token to record a platform configuration of the originator device; a user interface to allow the user to transmit a passphrase to the processor; a processor to generate a representation of the platform configuration; and a port to allow the device to communicate the representation to a registry service.
 7. The registry system of claim 6, wherein the fixed token further comprises a set of registers in which measurements of the originator device are recorded.
 8. The registry system of claim 6, wherein the registry is further to transmit an authentication token to the originator device.
 9. The registry system of claim 8, wherein the registry is further to store the representation and the authentication token.
 10. The registry system of claim 6, wherein the registry is further to validate requests from originators to interact with the registry.
 11. The registry system of claim 6, wherein the processor generates a representation of the platform configuration further comprises the processor applying a hash function to data values in platform configuration registers protected by the fixed token.
 12. A method of registering with a service, the method comprising: transmitting a user ID, passphrase and platform configuration values to a service; and providing a unique platform identifier to the service.
 13. The method of claim 12, wherein the unique platform identifier further comprises an RSA key.
 14. The method of claim 12, wherein the unique platform identifier further comprises an attestation identity key.
 15. The method of claim 12, wherein providing a unique platform identifier further comprises transmitting the unique platform identifier to the service initially.
 16. The method of claim 12, wherein providing a unique platform identifier further comprises transmitting the unique platform identifier in response to a request from the service.
 17. A method of allowing access to a service, the method comprising: receiving a request for an authentication nonce from a user; generating a nonce and returning it to the user; obtaining a credential from the user; verifying a signature within the credential; verifying a platform configuration value within the credential; and if the signature and platform configuration value are valid, returning a session token to the user.
 18. The method of claim 17, wherein the credential further comprises an attestation and a passphrase.
 19. The method of claim 18, wherein the method further comprises verifying the passphrase supplied by the user.
 20. The method of claim 17, wherein the credential further comprises an attestation nonce.
 21. The method of claim 20, wherein the method further comprises: retrieving the authentication nonce and a user passphrase from storage; and deriving the attestation nonce prior to verifying the signature.
 22. The method of claim 17, wherein a user passphrase, user ID and unique platform identifier have been previously validated.
 23. The method of claim 22, wherein the method further comprises retrieving the nonce and validating it prior to verifying the signature. 